I'm very sorry to hear of your sorrow butterfly.
Some points

1) She is not totally to blame. It takes two to tango no matter how he tries to justify it. What kind of an excuse is 'trying to prove he's a guy not a gay'? you're a woman yes? is it not proof enough that he has you? I would be insulted at that lame excuse.

2) If you forgive him and go back to him he WILL do this again. It's obvious he has no respect for you or his feelings, and doesn't deserve to be with a caring woman if this is how he's going to treat them. If in his eyes he 'got away with it', then he will think he can 'get away with it' again.
If you stand up for yourself and kick him to the curb he will think twice before breaking another girl's heart. Either way, the man you loved is gone.
Vow's are made on the condition of commitment from both sides, you didn't agree to be treated like this.

3) finally ponder the meaning behind this passage from a geeky little song. It's something that's helped to stop me getting hurt again and again.

And when we choose who to sleep with and reproduce
Our sexual choices affect the gene pool
So it’s simple, all we need to do is refuse
To sleep with mean people, and things will improve
Especially women – on you the pressure is greater
‘Cause men will always do what it takes to get into your favour
That’s just in our nature, so if selfish behaviour
Was a sexual graveyard, the effects would be major!